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• Does complex JOINs causes high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• SQL: Join multiple tables and get a grouped sum

  - by Scienceprodigy

  I have a database with 3 tables that have related data. One table has transactions, and the other two relate to transaction categories. Basically it's financial data, so each transaction has a category (i.e. "gasoline" for a gas purchase transaction). A short version of my Transactions table looks like this- Transactions Table: ________________________________ | ID | Type | Amount | Category | --------------------------------- I also have two more tables relating a category to a categories parent. So basically, every Category entry in the Transactions Table belongs to a parent category (i.e. "gasoline" would belong to say "Automotive Expenses"). For categories, and their parent, I have two tables - Category Children: ____________________________________________ | ID | Parent Category ID | Child Category | -------------------------------------------- Category Parent: ________________________ | ID | Parent Category | ------------------------ What I'm trying to do is query the database and have it return a total spending by parent category. To get "spending" the Type of transactions must be "Debit". I tried the following statement: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category = 'category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id = category_parents._id WHERE trans_type = 'Debit' GROUP BY parent_category ORDER BY totals DESC but it gives me the following exception: 12-31 13:51:21.515: ERROR/Exception on query(4403): android.database.sqlite.SQLiteException: no such column: category_children.parent_category_id: , while compiling: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category='category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id=category_parents._id where trans_type='Debit' group by parent_category order by totals desc Any help is appreciated. (EXTRA CREDIT: I also need to make another statement to do spending by child category, given the parent category)

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• Where do I start ?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be learning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• Access denied when trying to access my database.

  - by Sergio Tapia

  Here's my code: <html> <head> </head> <body> <?php $user = mysql_real_escape_string($_GET["u"]); $pass = mysql_real_escape_string($_GET["p"]); $query = "SELECT * FROM usario WHERE username = '$user' AND password = '$pass'"; mysql_connect(localhost, "root", ""); @mysql_select_db("multas") or die( "Unable to select database"); $result=mysql_query($query); if(mysql_numrows($result) > 0){ echo 'si'; } ?> </body> </html> And here's the error I get when I try to run it Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\useraccess.php on line 7 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in C:\xampp\htdocs\useraccess.php on line 7 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\useraccess.php on line 8 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in C:\xampp\htdocs\useraccess.php on line 8 Warning: mysql_numrows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\useraccess.php on line 16

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• Regular expression for finding non-breaking string names in code and then breaking them up for SQL q

  - by Rob Segal

  I am trying to devlop a regex for finding camel case strings in several code files I am working with so I can break them up into separate words for use in a SQL query. I have strings of the form... EmailAddress FirstName MyNameIs And I want them like this... Email Address First Name My Name Is An example SQL query which I currently have is... select FirstName, MyNameIs from MyTables I need the queries in the form... select FirstName as 'First Name', MyNameIs as 'My Name Is' from MyTables Any time a new capital letter appears that should be a new grouping which I can pick out of the matched string. I currently have the following regex... ([A-Z][a-z]+)+ Which does match the cases I have shown above but when I want to perform a replace I need to define groups. Currently I have tried... (([A-Z])([a-z]+))+ Which sort of works. It will pick out "Address" as the first grouping from "EmailAddress" as opposed to "Email" which is what I was expecting. No doubt there is something I'm misunderstanding here so any help is greatly appreciated.

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• SSH + MysqlDump Remote Backup Script

  - by bundini

  I'm trying to issue a remote mysqldump command, redirect stdout to a dmp file, then tar that up. I'm a bit confused as to how to do the redirection bits over ssh: i.e. ssh [email protected] mysqldump $dbname -u admin -p > dbdump.dmp && tar cvzf dbdump.tar.gz dbdump.dmp Issues: 1) I'm not providing the password because I want it to prompt me. Will an ssh remote command deal with this? 2) What's the deal with the syntax? Do I want to use quotations, or don't I? What happens with the redirects and pipes? Do those have to be escaped or formatted in some special fashion.

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• What information should a SVN/Versioned file commit comment contain?

  - by RenderIn

  I'm curious what kind of content should be in a versioned file commit comment. Should it describe generally what changed (e.g. "The widget screen was changed to display only active widgets") or should it be more specific (e.g. "A new condition was added to the where clause of the fetchWidget query to retrieve only active widgets by default") How atomic should a single commit be? Just the file containing the updated query in a single commit (e.g. "Updated the widget screen to display only active widgets by default"), or should that and several other changes + interface changes to a screen share the same commit with a more general description like ("Updated the widget screen: A) display only active widgets by default B) added button to toggle showing inactive widgets") I see subversion commit comments being used very differently and was wondering what others have had success with. Some comments are as brief as "updated files", while others are many paragraphs long, and others are formatted in a way that they can be queried and associated with some external system such as JIRA. I used to be extremely descriptive of the reason for the change as well as the specific technical changes. Lately I've been scaling back and just giving a general "This is what I changed on this page" kind of comment.

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• MySQL Connector: parameters not being added

  - by LookitsPuck

  Hey all! Looking at my query log for MySQL, I see my parameters aren't being added. Here's my code: MySqlConnection conn = new MySqlConnection(ApplicationVariables.ConnectionString()); MySqlCommand com = new MySqlCommand(); try { conn.Open(); com.Connection = conn; com.CommandText = String.Format(@"SELECT COUNT(*) AS totalViews FROM pr_postreleaseviewslog AS prvl WHERE prvl.dateCreated BETWEEN (@startDate) AND (@endDate) AND prvl.postreleaseID IN ({0})" , ids); com.CommandType = CommandType.Text; com.Parameters.Add(new MySqlParameter("@startDate", thisCampaign.Startdate)); com.Parameters.Add(new MySqlParameter("@endDate", endDate)); numViews = Convert.ToInt32(com.ExecuteScalar()); } catch (Exception ex) { } finally { conn.Dispose(); com.Dispose(); } Looking at the query log, I see this: SELECT COUNT(*) AS totalViews FROM pr_postreleaseviewslog AS prvl WHERE prvl.dateCreated BETWEEN (@startDate) AND (@endDate) AND prvl.postreleaseID IN (1,2) I've used the MySQL .NET connector on countless projects (I actually have a base class that takes care of opening these connections, and closing them with transactions, etc.). However, I took over this application, and here I am now. Thanks for the help!

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• How to configure sudoers with path wildcards?

  - by C. Lee

  I need sudo for a command for any path under a particular area. Example: sudo mycommand /opt/apps/myapp/... What is the sudoers syntax to allow this command to run in any path that falls under /opt/apps/myapp? This is Solaris 10 sudo. Thank you for your reply, but I don't need wildcards for the path to the commands, but wildcards for the arguments for the commands. For example, we want to do something like... sudo mycmd /opt/userarea/area1 sudo mycmd /opt/userarea/area1/area2 sudo mycmd /opt/userarea/area1/area2/area3 So far, using wildcards for the arguments in sudoers look like this: /opt/userarea/* /opt/userarea/*/* And it seems like if we want to have N levels of directories, then we need N lines in sudoers! Is there a better way to include all N levels in one line in sudoers? Thanks.

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• Handle row deletion in UITableViewController

  - by Kamchatka

  Hello, I hava a UINavigationController. The first level is a UITableViewController, the second level just shows details on one of the items of the table view. In this detail view, I can delete the item. It deletes the underlying managed object. When I pop back to the view, I have a crash. I understand why, it's because I didn't update the cached array that contains the data. I looked at several tutorials and I don't exactly understand how am I supposed to handle deletion. Maybe I don't understand exactly where I should fetch the objects in the model. Should I do a query for every cellForRowAtIndexPath and take the item in the result at position indexPath.row? It doesn't look efficient. Should I check for changes somewhere and recache the whole query in an array. I would think CoreData would provide something more natural but I couldn't find it so far. Thanks in advance.

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• code to ping websites works sometimes ...

  - by trustfundbaby

  I'm testing out a piece of code to ping a bunch of websites I own on a regular basis, to make sure they're up. I'm using rails and so far I have this hideous test action that I'm using to try it out (see below). The problem though, is that sometimes it works, and other times it won't ... sometimes it runs through the code just fine, other times, it seems to completely ignore the begin/rescue block ... a. I need help figuring out what the problem is b. And refactoring this to make it look respectable. Your help is much appreciated. require 'net/http' require 'uri' def ping @sites = NewsSource.all @sites.each do |site| if site.uri and !site.uri.empty? uri = URI.parse(site.uri) response = nil path = uri.path.blank? ? '/' : uri.path path = uri.query.blank? ? path : "#{path}?#{uri.query}" begin Net::HTTP.start(uri.host, uri.port) {|http| http.open_timeout = 30 http.read_timeout = 30 response = http.head(path) } if response.code.eql?('200') or response.code.eql?('301') or response.code.eql?('302') site.up = true else site.up = false end site.up_check_msg = response.message site.up_check_code = response.code rescue Errno::EBADF rescue Timeout::Error site.up = false site.up_check_msg = 'timeout' site.up_check_code = '408' end site.up_check_time = 0.seconds.ago site.save end end end

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• kvm -net only passing broadcast, multicast, and guest destination traffic

  - by user52874

  Figured this out just last week, but I can't find it now. Even printed it out. Can't find that either. Frustrating...so...help! Configured a 'monitoring' nic on a kvm guest (running 'Security Onion, if it matters). I read (somewhere) that the default nic configuration for a kvm guest is to only pass broadcast traffic, multicast traffic, and traffic with the guest's mac as a destination. There is an option to override this behaviour, and pass all traffic. It's something like --mac-filtering=no, or --mac-restriction=no, or something like that. Worked beautifully. Does this look at all familiar to anyone who can clue me in to the exact option syntax? thx.

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• What's the best way to select max over multiple fields in SQL?

  - by allyourcode

  The I kind of want to do is select max(f1, f2, f3). I know this doesn't work, but I think what I want should be pretty clear (see update 1). I was thinking of doing select max(concat(f1, '--', f2 ...)), but this has various disadvantages. In particular, doing concat will probably slow things down. What's the best way to get what I want? update 1: The answers I've gotten so far aren't what I'm after. max works over a set of records, but it compares them using only one value; I want max to consider several values, just like the way order by can consider several values. update 2: Suppose I have the following table: id class_name order_by1 order_by_2 1 a 0 0 2 a 0 1 3 b 1 0 4 b 0 9 I want a query that will group the records by class_name. Then, within each "class", select the record that would come first if you ordered by order_by1 ascending then order_by2 ascending. The result set would consist of records 2 and 3. In my magical query language, it would look something like this: select max(* order by order_by1 ASC, order_by2 ASC) from table group by class_name

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• How to make safe frequent DataSource switches for AbstractRoutingDataSource?

  - by serg555

  I implemented Dynamic DataSource Routing for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query. Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use: public class CustomerContextHolder { private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>(); public static void setCustomerType(CustomerType customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType); } public static CustomerType getCustomerType() { return (CustomerType) contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } } It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel: CustomerContextHolder.setCustomerType(CustomerType.GOLD); //<another user will switch customer type here to CustomerType.SILVER in another request> List<Item> goldItems = catalog.getItems(); Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true. How to make sure that nobody else will switch datasource until I run required query for current user? Thanks.

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• FluentNHibernate, getting 1 column from another table

  - by puffpio

  We're using FluentNHibernate and we have run into a problem where our object model requires data from two tables like so: public class MyModel { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual int FooId { get; set; } public virtual string FooName { get; set; } } Where there is a MyModel table that has Id, Name, and FooId as a foreign key into the Foo table. The Foo tables contains Id and FooName. This problem is very similar to another post here: http://stackoverflow.com/questions/1896645/nhibernate-join-tables-and-get-single-column-from-other-table but I am trying to figure out how to do it with FluentNHibernate. I can make the Id, Name, and FooId very easily..but mapping FooName I am having trouble with. This is my class map: public class MyModelClassMap : ClassMap<MyModel> { public MyModelClassMap() { this.Id(a => a.Id).Column("AccountId").GeneratedBy.Identity(); this.Map(a => a.Name); this.Map(a => a.FooId); // my attempt to map FooName but it doesn't work this.Join("Foo", join => join.KeyColumn("FooId").Map(a => a.FooName)); } } with that mapping I get this error: The element 'class' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'join' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'joined-subclass, loader, sql-insert, sql-update, sql-delete, filter, resultset, query, sql-query' in namespace 'urn:nhibernate-mapping-2.2'. any ideas?

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• Exception on inserting into Access 2010 in C Sharp

  - by slao.it

  Hello, I am getting this exception when inserting into a Access 2010 database. Ex: System.Data.OleDb.OleDbException (0x80040E14): Syntax error in string in query expression ''CityName ?'. at System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling(OleDbHResult hr) at System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult(tagDBPARAMS dbParams, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommandText(Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteCommand(CommandBehavior behavior, Object& executeResult) at System.Data.OleDb.OleDbCommand.ExecuteReaderInternal(CommandBehavior behavior, String method) at System.Data.OleDb.OleDbCommand.ExecuteNonQuery() at ReadingData.Program.Main(String[] args) in C:\Users\user\documents\visual studio 2010\Projects\ReadingData\ReadingData\Program.cs:line 238 INSERT INTO CranbrookMain (ID,BlockNo,Plot,SubPlot,Code,Type,LastName,FirstName,ServiceHome,ServiceAddress,ServiceCity,Notes) VALUES ('1','Y','37','DS','C2','O','SMITH','John','Service Inc.','520B SLATER ROAD N.W.','CityName','CityName ? ') insertSQL = "INSERT INTO CranbrookMain (ID,BlockNo,Plot,SubPlot,Code,Type,LastName," + "FirstName,ServiceHome,ServiceAddress,ServiceCity,Notes) VALUES (" + "'"+id+ "','" + blockNo + "','" + plot + "','" + subPlot + "','" + code + "','" + type + "','" + lastname + "','" + firstname + "','" + serviceHome + "','" + serviceAddress + "','" + serviceCity + "','" + notes +"')"; Console.WriteLine(); OleDbCommand cmd = new OleDbCommand(insertSQL, con); // creating query command cmd.ExecuteNonQuery(); The error occurs in cmd.ExecuteNonQuery() function call. The above SQL INSERT statement works fine if I directly execute in the Access 2010 file.

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• Select those objects whose related objects IDs are *all* in given string

  - by Jannis

  Hi Django people, I want to build a frontend to a recipe database which enables the user to search for a list of recipes which are cookable with the ingredients the user supplies. I have the following models class Ingredient(models.Model): name = models.CharField(max_length=100, unique=True) slug = models.SlugField(max_length=100, unique=True) importancy = models.PositiveSmallIntegerField(default=4) […] class Amount(models.Model): recipe = models.ForeignKey('Recipe') ingredient = models.ForeignKey(Ingredient) […] class Rezept(models.Model): name = models.CharField(max_length=100) slug = models.SlugField() instructions = models.TextField() ingredients = models.ManyToManyField(Ingredient, through=Amount) […] and a rawquery which does exactly what I want: It gets all the recipes whose required ingredients are all contained in the list of strings that the user supplies. If he supplies more than necessary, it's fine too. query = "SELECT *, COUNT(amount.zutat_id) AS selected_count_ingredients, (SELECT COUNT(*) FROM amount WHERE amount.recipe_id = amount.id) AS count_ingredients FROM amount LEFT OUTER JOIN amount ON (recipe.id = recipe.recipe_id) WHERE amount.ingredient_id IN (%s) GROUP BY amount.id HAVING count_ingredient=selected_count_ingredient" % ",".join([str(ingredient.id) for ingredient in ingredients]) rezepte = Rezept.objects.raw(query) Now, what I'm looking for is a way that does not rely on .raw() as I would like to do it purely with Django's queryset methods. Additionally, it would be awesome if you guys knew a way of including the ingredient's importancy in the lookup so that a recipe is still shown as a result even though one of its ingredients (that has an importancy of 0) is not supplied by the user.

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• Call to a member function num_rows() on a non-object

  - by Patrick

  I need to get the number of rows of a query (so I can paginate results). As I'm learning codeigniter (and OO php) I wanted to try and chain a -num_rows() to the query, but it doesn't work: //this works: $data['count'] = count($this->events->findEvents($data['date'], $data['keyword'])); //the following doesn't work and generates // Fatal Error: Call to a member function num_rows() on a non-object $data['count2'] = $this->events->findEvents($data['date'], $data['keyword'])->num_rows(); the model returns an array of objects, and I think this is the reason why I can't use a method on it. function findEvents($date, $keyword, $limit = NULL, $offset = NULL) { $data = array(); $this->db->select('events.*, venues.*, events.venue AS venue_id'); $this->db->join('venues', 'events.venue = venues.id'); if ($date) { $this->db->where('date', $date); } if ($keyword) { $this->db->like('events.description', $keyword); $this->db->or_like('venues.description', $keyword); $this->db->or_like('band', $keyword); $this->db->or_like('venues.venue', $keyword); $this->db->or_like('genre', $keyword); } $this->db->order_by('date', 'DESC'); $this->db->order_by('events.priority', 'DESC'); $this->db->limit($limit, $offset); //for pagination purposes $Q = $this->db->get('events'); if ($Q->num_rows() > 0) { foreach ($Q->result() as $row) { $data[] = $row; } } $Q->free_result(); return $data; } Is there anything that i can do to be able to use it? EG, instead of $data[] = $row; I should use another (OO) syntax?

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• Make shortened and long urls play together on the same domain (RewriteRule).

  - by Renato Renato

  Long story short, I want to have both example.com/aJ5 and example.com/any-other-url working together. I'm using apache and not very good at writing regex. I have already a global RewriteRule which sends everything to the app entry point. What I need is to tell apache if length($path) is <= 5 chars then rewrite to another location. I know I can use {1,5} like syntax in regex, but don't really know if it's what I'm looking for. I'd like to implement this at web-server level rather than php level. Any help is appreciated.

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• Where should I put contextual data related to an Object that is not really a property of the object?

  - by RenderIn

  I have a Car class. It has three properties: id, color and model. In a particular query I want to return all the cars and their properties, and I also want to return a true/false field called "searcherKnowsOwner" which is a field I calculate in my database query based on whether or not the individual conducting the search knows the owner. I have a database function that takes the ID of the searcher and the ID of the car and returns a boolean. My car class looks like this (pseudocode): class Car{ int id; Color color; Model model; } I have a screen where I want to display all the cars, but I also want to display a flag next to each car if the person viewing the page knows the owner of that car. Should I add a field to the Car class, a boolean searcherKnowsOwner? It's not a property of the car, but is actually a property of the user conducting the search. But this seems like the most efficient place to put this information.

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• MySql too many connections

  - by MichaelMcCabe

  I hate to bring up a question which is widely asked on the web, but I cant seem to solve it. I started a project a while back and after a month of testing, I hit a "Too many connections" error. I looked into it, and "Solved" it by increasing the max_connections. This then worked. Since then more and more people started to use it, and it hit again. When I am the only user on the site, i type "show processlist" and it comes up with about 50 connections which are still open (saying "Sleep" in the command). Now, I dont know enough to speculate why these are open, but in my code I tripple checked and every connection I open, I close. ie. public int getSiteIdFromName(String name, String company)throws DataAccessException,java.sql.SQLException{ Connection conn = this.getSession().connection(); Statement smt = conn.createStatement(); ResultSet rs=null; String query="SELECT id FROM site WHERE name='"+name+"' and company_id='"+company+"'"; rs=smt.executeQuery(query); rs.next(); int id=rs.getInt("id"); rs.close(); smt.close(); conn.close(); return id; } Every time I do something else on the site, another load of connections are opened and not closed. Is there something wrong with my code? and if not, what could be the problem?

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• Do complex JOINs cause high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• SQL Distinct keyword in assignment statement

  - by Brandi

  I have a query that works: DECLARE @ProductID int SET @ProductID = '1234' SELECT DISTINCT TOP 12 a.ProductID FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE b.ProductID = @ProductID) AND a.ProductID != @ProductID It returns a list of 12 product numbers, all unique. I need to store these results in a variable, comma separated, because that's what 3rd party stored procedure needs. So I have this: DECLARE @ProductID int DECLARE @relatedprods varchar(8000) SET @ProductID = '1234' SET @relatedprods = '' SELECT TOP 12 @relatedprods = @relatedprods + CONVERT(VARCHAR(20), a.ProductID) + ', ' FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE B.ProductID = @ProductID) AND a.ProductID != @ProductID SELECT @relatedprods Now, none of these are distinct, but it is returning 12 rows. Now I add the 'distinct' back in, like in the first query: DECLARE @ProductID int DECLARE @relatedprods varchar(8000) SET @ProductID = '1234' SET @relatedprods = '' SELECT DISTINCT TOP 12 @relatedprods = @relatedprods + CONVERT(VARCHAR(20), a.ProductID) + ', ' FROM A a WHERE a.CategoryID IN (SELECT b.CategoryID FROM B b WHERE B.ProductID = @ProductID) AND a.ProductID != @ProductID SELECT @relatedprods Only one product is returned in the comma separated list! Does 'distinct' not work in assignment statements? What did I do wrong? Or is there a way to get around this? Thanks in advance!

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• FTP "PUT" fails from Virtual Machine, but not host PC: 504 Command not implemented for that paramete

  - by BrianH

  I have an FTP Script I'm using to automate a file transfer. The transfer works fine on my PC (XP SP2), but when I try and run it on a VM on my PC (XP SP2), the "put" commands gives off: 504 Command not implemented for that parameter. FTP File: open [ftp site] [username] [password] cd [directory on FTP server] binary hash put ..\[subfolder1]\[Subfolder2]\[subfolder3]\[filename] bye The FTP site/server is around the world, and not under my control. From what I understand of a 504, that means the command should NEVER work, but since the same script DOES work on my PC (hosting the VM), that eliminates syntax, file naming, etc. The put command when triggered from the VM, actually creates a 0 length file on the target FTP server, but doesn't populate the file.

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• How do I grab and use a variables coming back through ValueList from an AJAX call?

  - by Mel

  I'm trying the following code to execute a search and it's not working. On the search.cfm page, the only value coming back is the value I input into the search field (even if I click an autosuggest value, it's not coming back; only the letters I actually type myself come back). <cfform class="titleSearchForm" id="searchForm" action="search.cfm?GameID=#cfautosuggestvalue.GameID#" method="post"> <fieldset> <cfinput type="text" class="titleSearchField" name="TitleName" onChange="form.submit()" autosuggest="cfc:gz.cfcomp.search.AutoSuggestSearch({cfautosuggestvalue})"> <input type="button" class="titleSearchButton" value=" " /> </fieldset> </cfform> Query in CFC: <cfquery name="SearchResult" datasource="myDSN"> SELECT CONCAT(titles.TitleName, ' on ', platforms.PlatformAbbreviation) AS sResult, games.GameID FROM games Inner Join platforms ON games.PlatformID = platforms.PlatformID Inner Join titles ON titles.TitleID = games.TitleID WHERE UCase(titleName) LIKE Ucase('#ARGUMENTS.SearchString#%') ORDER BY titleName ASC; </cfquery> Two things: First of all, I would like to get the GameID back to the page making the AJAX request; I know why it is not coming back: Because I'm only returning sResult var, which does not include the GameID. Is there a way to return the GameID value without displaying it? The second thing: How to I grab a value from the auto-suggest once it is returned? Say I want to grab the GameID, or if I can't do that, the "TitleName" to use that in my query? I tried passing it to the form this way: action="search.cfm?GameID=#cfautosuggestvalue.GameID#" - but that does not work. How do I reference the autosuggestionvalue varaibles for use? Thanks

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